Neoview SQL Reference Manual (R2.2)

Considerations
• “Case Considerations” (page 105)
• “Number Considerations” (page 105)
• “Formatted [OPTIONS 'f'] Considerations” (page 105)
• “Normal User [OPTIONS 'n'] Considerations” (page 106)
• “Expert User [OPTIONS 'e'] Considerations” (page 108)
• “Machine-Readable [OPTIONS 'm'] Considerations” (page 110)
Case Considerations
In most cases, words in the commands can be in uppercase or lowercase. The options letter must
be single quoted and in lowercase.
Number Considerations
Costs are given in a generic unit of effort. They show relative costs of an operation.
When numbers are displayed as 0.01 for OPTIONS ‘n’ (or 0.0001 for OPTIONS ‘e’), the numbers
have likely been rounded up and are usually much smaller than shown. However, if the numbers
are zero, the display shows “0”.
When trailing decimal digits are zero, they are dropped. For example, 6.4200 would display as
6.42 and 5.0 would display as 5, without a decimal point.
Formatted [OPTIONS 'f'] Considerations
The formatted option is the simplest option. It provides essential, brief information about the
plan and shows the operators and their order within the query execution plan.
OPTIONS 'f' formats the EXPLAIN output into these fields:
Left child sequence numberLC
Right child sequence numberRC
The sequence number of the operator in the query planOP
The operator typeOPERATOR
Query optimizations that were appliedOPT
Additional information about the operatorDESCRIPTION
Estimated number of rows returned by the plan. CARDINALITY and
ROWS_OUT are the same.
CARD
This example uses OPTIONS 'f':
>>explain options 'f' select * from region;
LC RC OP OPERATOR OPT DESCRIPTION CARD
--- --- --- -------------------- -------- -------------------- ---------
3 . 4 root 5.00E+000
2 . 3 split_top 1:64(hash2) 5.00E+000
1 . 2 partition_access 5.00E+000
. . 1 file_scan fs fr REGION 5.00E+000
--- SQL operation complete.
To use the EXPLAIN statement with a prepared statement, first prepare the query. Then use the
EXPLAIN statement:
EXPLAIN Statement 105